Hydrogen sulfide affects the performance of a methanogenic bioelectrochemical system used for biogas upgrading.

ABSTRACT

Methanogenic bioelectrochemical systems (BESs) can convert carbon dioxide (CO2) to methane (CH4) and may be used for anaerobic digester biogas upgrading. However, the effect of hydrogen sulfide (H2S), a common biogas component, on BES performance is unknown. Thus, the objective of this study was to assess the effect of H2S addition to the cathode headspace on BES performance at a range of initial gas-phase H2S concentrations (0-6% v/v), as well as its effect on the anode and cathode microbial communities. As the initial cathode headspace H2S increased from 0 to 2% (v/v), biocathodic CH4 production increased by two-fold to 3.56 ± 0.36 mmol/L-d, due to dissolved H2S transport from the cathode to the anode where H2S was oxidized. Elemental sulfur and sulfate were H2S oxidation products detected in the anode. Above 3% initial cathode headspace H2S, biocathodic CH4 production declined due to inhibition. A phylotype most closely related to Methanobrevibacter arboriphilus dominated the cathode archaeal communities. In the sulfide-amended BES, a phylotype similar to the exoelectrogen Ochrobactrum anthropi was enriched in both the anode and cathode, whereas phylotypes related to sulfate-reducing and sulfur oxidizing Bacteria were detected in the bioanode. Thus, sulfide transport and oxidation in the anode play an important role in methanogenic BESs treating sulfide-bearing biogas.